For me the reason for Teela abandoning everyone she knew was pretty unbelievable, but then I never really watched the original series so idk the backstory much.
No, that was unbelievable. A father and mother (who only minutes prior promoted her to the highest rank in the military because of how strong, honourable and competent she is) just lost their son and her response is fuck you, I quit and turn my back on everyone because you didn't tell me He-Man's identity.